A typical prior art syringe includes a hollow syringe body, a plunger slidably received within one end of the hollow body, and a needle connected to the other end of the hollow body. The plunger is moved through the syringe body to, in turn, eject through the needle the medicament or other substance contained within the syringe. The syringe body typically defines a transparent, graduated cylinder, and the user visually aligns the plunger tip with the appropriate graduation to dispense a desired amount of medicament or other substance from the syringe. One of the drawbacks associated with this type of syringe is that physicians, practitioners and other users may become tired, have difficulty focusing on the graduations, and/or may shake or otherwise have difficulty precisely aligning the plunger with the correct graduation(s) on the syringe body. As a result, human error or physical impairment can easily cause a user to dispense the incorrect amount of medicament or other substance from the syringe, and similarly prevent a user from precisely metering a constant dosage from one application to the next. When dispensing medicaments, accurate and controlled delivery is critical, particularly for avoiding overmedication. Overmedication can especially occur when the medicament is in the form of a liquid or other type of fluid.
Several devices described in the prior art permit controlled doses of medicaments to be delivered. These devices can be complicated to manufacture, assemble and fill with medicaments. As a result, these devices can be expensive to manufacture and may not be useful for vaccines, over the counter (“OTC”) medicaments, and other types of pharmaceutical preparations. Another disadvantage of these prior art devices is that air can enter the device during filling and/or storage after the device is filled. Air entering the device during filling or storage can cause degradation of the medicament or other substance contained therein, reducing the efficacy of the medicament or other substance, and/or causing spoilage which may require that the medicament or other substance be discarded.
For some medicaments, preservatives are added to prevent degradation or spoilage of the medicament before use due to ingress of air or other contaminants. The preservatives can react with the medicament, however, reducing its efficacy. Also, some users can have undesirable adverse reactions to the preservatives in the medicaments.
Accordingly, it is an object of a currently preferred embodiment the present invention to provide a syringe that can be filled with a sterile substance, such as a vaccine, medicament or other pharmaceutical preparation, while maintaining the sterility of the syringe and substance during filling and storage thereafter. It is yet another object of a currently preferred embodiment of the present invention to provide a syringe with a heat sealable and/or fusible stopper on the plunger that prevents ingress of air or other contaminants through the plunger and into the substance contained within the syringe.
It is also an object of a currently preferred embodiment of the present invention to provide a syringe including means for providing a metered dose of a substance contained within the syringe, such as a vaccine, medicament or pharmaceutical preparation. It is another object of a currently preferred embodiment of the present invention to provide a syringe that can be relatively inexpensive to manufacture, easy-to-use and that provides a metered dose of a vaccine or other medicament, pharmaceutical preparation or other substance.
It is an object of another currently preferred embodiment of the present invention to provide a reconstitution syringe including multiple chambers for storing multi-component substances, such as vaccines, and other medicaments and pharmaceutical preparations, whereby the components can be mixed immediately prior to use and metered doses of such substances can be dispensed from the syringe.